An aneurysm is a localized, blood-filled dilation or bulge of a blood vessel caused by disease or weakening of the vessel wall. Aneurysms can occur anywhere where there are blood vessels, although they are most common in arteries. Aneurysms most commonly occur in arteries at the base of the brain, in the circle of Willis and in the aorta. Rupture and blood clotting are the risks involved with aneurysms. Particularly if the patient has elevated blood pressure, this bulge in the blood vessel can burst and lead to hemorrhage and possibly death at any time. The risk of death is high except for rupture in the extremities. The larger an aneurysm becomes, the more likely it is to burst.
X-ray C-arms are routinely used in medicine to acquire images for diagnostic assessment of a patient's vascular structures, and for guidance of interventional therapeutic procedures such as stent placement or coiling of aneurysms. Cerebral aneurysms are usually treated with stents, wire coils or glue, with the intention to form a blood clot in the aneurysm that relieves the pressure against the aneurysm's wall.
Diagnostic applications include the acquisition of angiograms, 2D X-ray projection images of vascular structures filled with a contrast agent injected through a catheter. For an improved representation of the vessels under examination, Digital Subtraction Angiography (DSA) has been developed. DSA is fluoroscopy technique used in interventional radiology to clearly visualize blood vessels in a bony or dense soft tissue environment. Images are produced by subtracting a ‘pre-contrast image’ or the mask from subsequent images acquired after the contrast medium has been introduced into a structure or tissue of interest. These images can be used to provide time-resolved or time-varying information that shows the development of the structure or tissue of interest over time.
Identifying physical properties of an aneurysm, such as the thickness, rigidity and pliability of the vessel wall, can yield additional information for assessing the risk of the aneurysm, monitoring and treatment thereof. Physical properties derived by most prior work are static, and fail to take into account temporal changes that occur during a cardiac cycle. Currently, there is very little work known to be capable of providing three-dimensional (3D) reconstruction and representation of dynamic aneurysm wall motion.